BackgroundWhite matter hyperintensity (WMH) burden may lead to poor clinical outcomes after endovascular thrombectomy (EVT). But the relationship between WMH burden and cerebral edema (CED) is unclear.PurposeTo examine the association between WMH burden and CED and functional outcome in patients treated with EVT.Study TypeRetrospective.Subject344 patients with acute anterior circulation large‐vessel occlusion stroke who received EVT at two comprehensive stroke centers. Mean age was 62.6 ± 11.6 years and 100 patients (29.1%) were female.Field Strength/Sequence3T, including diffusion‐weighted imaging and fluid‐attenuated inversion recovery (FLAIR) images.AssessmentThe severity of WMH was evaluated using the Fazekas scale on a FLAIR sequence before EVT. The severity of CED was assessed using CED score (three for malignant cerebral edema [MCE]) and net water uptake (NWU)/time on post‐EVT cranial CT. The impact of WMH burden on MCE, NWU/time, and 3‐month poor outcome (modified Rankin scale >2) after EVT were assessed.Statistical TestsPearson's chi‐squared test, Fisher exact test, 2‐tailed t test, Mann–Whitney U test, multivariable logistic regression, multivariate regression analysis, Sobel test. A P value <0.05 was considered statistically significant.ResultsWMH burden was not significantly associated with MCE and parenchymal hemorrhage (PH) in the whole population (P = 0.072; P = 0.714). WMH burden was significantly associated with an increased risk of MCE (OR, 1.550; 95% CI, 1.128–2.129), higher NWU/time (Coefficient, 0.132; 95% CI, 0.012–0.240), and increased risk of 3‐month poor outcome (OR, 1.434; 95% CI, 1.110–1.853) in the subset of patients without PH. Moreover, the connection between WMH burden and poor outcome was partly mediated by CED in patients without PH (regression coefficient changed by 29.8%).Data ConclusionWMH burden is associated with CED, especially MCE, and poor outcome in acute ischemic stroke patients treated with EVT. The association between WMH burden and poor outcome may partly be attributed to postoperative CED.Level of Evidence3.Technical EfficacyStage 5.